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使用JAVA實(shí)現(xiàn)http通信詳解

更新時(shí)間：2015年08月14日 10:41:40 投稿：hebedich

本文給大家匯總介紹了幾種java實(shí)現(xiàn)http通訊的方法，非常的簡(jiǎn)單實(shí)用，有需要的小伙伴可以參考下。

Http通信概述

Http通信主要有兩種方式POST方式和GET方式。前者通過Http消息實(shí)體發(fā)送數(shù)據(jù)給服務(wù)器，安全性高，數(shù)據(jù)傳輸大小沒有限制，后者通過URL的查詢字符串傳遞給服務(wù)器參數(shù)，以明文顯示在瀏覽器地址欄，保密性差，最多傳輸2048個(gè)字符。但是GET請(qǐng)求并不是一無是處——GET請(qǐng)求大多用于查詢（讀取資源），效率高。POST請(qǐng)求用于注冊(cè)、登錄等安全性較高且向數(shù)據(jù)庫中寫入數(shù)據(jù)的操作。

除了POST和GET，http通信還有其他方式！請(qǐng)參見http請(qǐng)求的方法

編碼前的準(zhǔn)備

在進(jìn)行編碼之前，我們先創(chuàng)建一個(gè)Servlet，該Servlet接收客戶端的參數(shù)(name和age)，并響應(yīng)客戶端。

@WebServlet(urlPatterns={"/demo.do"})
public class DemoServlet extends HttpServlet {

  private static final long serialVersionUID = 1L;

  public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

    request.setCharacterEncoding("utf-8");
    response.setContentType("text/html;charset=utf-8");
    String name = request.getParameter("name");
    String age = request.getParameter("age");
    PrintWriter pw = response.getWriter();
    pw.print("您使用GET方式請(qǐng)求該Servlet。<br />" + "name = " + name + ",age = " + age);
    pw.flush();
    pw.close();
  }

  public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

    request.setCharacterEncoding("utf-8");
    response.setContentType("text/html;charset=utf-8");
    String name = request.getParameter("name");
    String age = request.getParameter("age");
    PrintWriter pw = response.getWriter();
    pw.print("您使用POST方式請(qǐng)求該Servlet。<br />" + "name = " + name + ",age = " + age);
    pw.flush();
    pw.close();
  }

}

使用JDK實(shí)現(xiàn)http通信

使用URLConnection實(shí)現(xiàn)GET請(qǐng)求

實(shí)例化一個(gè)java.net.URL對(duì)象；
通過URL對(duì)象的openConnection()方法得到一個(gè)java.net.URLConnection;
通過URLConnection對(duì)象的getInputStream()方法獲得輸入流；
讀取輸入流；
關(guān)閉資源。

public void get() throws Exception{

  URL url = new URL("http://127.0.0.1/http/demo.do?name=Jack&age=10");
  URLConnection urlConnection = url.openConnection();                          // 打開連接
  BufferedReader br = new BufferedReader(new InputStreamReader(urlConnection.getInputStream(),"utf-8")); // 獲取輸入流
  String line = null;
  StringBuilder sb = new StringBuilder();
  while ((line = br.readLine()) != null) {
    sb.append(line + "\n");
  }

  System.out.println(sb.toString());
}

使用HttpURLConnection實(shí)現(xiàn)POST請(qǐng)求

java.net.HttpURLConnection是java.net.URL的子類，提供了更多的關(guān)于http的操作（getXXX 和 setXXX方法）。該類中定義了一系列的HTTP狀態(tài)碼：

public void post() throws IOException{

  URL url = new URL("http://127.0.0.1/http/demo.do");
  HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();

  httpURLConnection.setDoInput(true);
  httpURLConnection.setDoOutput(true);    // 設(shè)置該連接是可以輸出的
  httpURLConnection.setRequestMethod("POST"); // 設(shè)置請(qǐng)求方式
  httpURLConnection.setRequestProperty("charset", "utf-8");

  PrintWriter pw = new PrintWriter(new BufferedOutputStream(httpURLConnection.getOutputStream()));
  pw.write("name=welcome");          // 向連接中輸出數(shù)據(jù)（相當(dāng)于發(fā)送數(shù)據(jù)給服務(wù)器）
  pw.write("&age=14");
  pw.flush();
  pw.close();

  BufferedReader br = new BufferedReader(new InputStreamReader(httpURLConnection.getInputStream(),"utf-8"));
  String line = null;
  StringBuilder sb = new StringBuilder();
  while ((line = br.readLine()) != null) {  // 讀取數(shù)據(jù)
    sb.append(line + "\n");
  }

  System.out.println(sb.toString());
}

使用httpclient進(jìn)行http通信

httpclient大大簡(jiǎn)化了JDK中http通信的實(shí)現(xiàn)。

maven依賴：

<dependency>
  <groupId>org.apache.httpcomponents</groupId>
  <artifactId>httpclient</artifactId>
  <version>4.3.6</version>
</dependency>

GET請(qǐng)求

public void httpclientGet() throws Exception{

  // 創(chuàng)建HttpClient對(duì)象
  HttpClient client = HttpClients.createDefault();

  // 創(chuàng)建GET請(qǐng)求（在構(gòu)造器中傳入U(xiǎn)RL字符串即可）
  HttpGet get = new HttpGet("http://127.0.0.1/http/demo.do?name=admin&age=40");

  // 調(diào)用HttpClient對(duì)象的execute方法獲得響應(yīng)
  HttpResponse response = client.execute(get);

  // 調(diào)用HttpResponse對(duì)象的getEntity方法得到響應(yīng)實(shí)體
  HttpEntity httpEntity = response.getEntity();

  // 使用EntityUtils工具類得到響應(yīng)的字符串表示
  String result = EntityUtils.toString(httpEntity,"utf-8");
  System.out.println(result);
}

POST請(qǐng)求

public void httpclientPost() throws Exception{

  // 創(chuàng)建HttpClient對(duì)象
  HttpClient client = HttpClients.createDefault();

  // 創(chuàng)建POST請(qǐng)求
  HttpPost post = new HttpPost("http://127.0.0.1/http/demo.do");

  // 創(chuàng)建一個(gè)List容器，用于存放基本鍵值對(duì)（基本鍵值對(duì)即：參數(shù)名-參數(shù)值）
  List<BasicNameValuePair> parameters = new ArrayList<>();
  parameters.add(new BasicNameValuePair("name", "張三"));
  parameters.add(new BasicNameValuePair("age", "25"));

  // 向POST請(qǐng)求中添加消息實(shí)體
  post.setEntity(new UrlEncodedFormEntity(parameters, "utf-8"));

  // 得到響應(yīng)并轉(zhuǎn)化成字符串
  HttpResponse response = client.execute(post);
  HttpEntity httpEntity = response.getEntity();
  String result = EntityUtils.toString(httpEntity,"utf-8");
  System.out.println(result);
}

HttpClient是Apache Jakarta Common下的子項(xiàng)目，用來提供高效的、最新的、功能豐富的支持HTTP協(xié)議的客戶端編程工具包，并且它支持HTTP協(xié)議最新的版本和建議。HttpClient已經(jīng)應(yīng)用在很多的項(xiàng)目中，比如Apache Jakarta上很著名的另外兩個(gè)開源項(xiàng)目Cactus和HTMLUnit都使用了HttpClient。

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